While we hear of the TARDIS having engines that are implicitly essential to it working, we’ve also see a TARDIS work without the rest of the machine.
“The Doctor’s Wife” and “Inferno” show that a TARDIS is capable of operating as just the console, which would seem to imply that they’re just a power source to allow the console to do its thing and move the whole ship around, or to allow for the pilot to do silly things like tow an entire planet one second out of phase.
Given that dimensionally transcendental engineering is integral to TARDIS design, the engines - and pretty much all of the rest of the interior - could be inside the console - even if they are also accessible via other rooms and corridors.
And the console, like the TARDIS itself, could be bigger on the inside. So while we see a console, who knows what’s happening inside of it
My take, informed mainly by The Doctor’s Wife, is that while a TARDIS console alone can move through time and space, it’s a bit like driving a card without a windshield, exhaust system, shocks and brakes. It may get you where you’re going, but the odds of you experiencing harm increase greatly.
